The default behavior of WordPress is to pull the union of multiple categories rather than the intersection. So, for example, ?cat=3,4 will show all items tagged to categories three and four. I think most people would expect this to be the reverse.

iSusi from Korea has a nice little plugin to fix this. InterCat sets the default behavior to generate, without additional joins, intersected category lists. Great for using WordPress to publish select streams of data to different sites.

This is an excellent way to find a chunk of HTML with regex. It finds specific table rows containing either “String1” or “String2”, regardless of linefeeds, carriage returns, or other nefarious forms of whitespace.